CO2 cycloaddition over ionic liquid immobilized hybrid zeolitic imidazolate frameworks: Effect of Lewis acid/base sites. (6th April 2021)

• Record Type: Journal Article
• Authors: Xiang, Wenlong; Shen, Chenyang; Lu, Zhe; Chen, Si; Li, Xiang; Zou, Rui; Zhang, Yueping; Liu, Chang-jun
• Is Part Of: Chemical engineering science. Volume 233(2021)
• Publication Date: 2021-04-06
• Subjects: Catalyst -- CO2 -- Cycloaddition -- Zeolitic imidazolate frameworks -- Ionic liquids; Chemical engineering -- Periodicals; Génie chimique -- Périodiques; Chemical engineering; Periodicals; Electronic journals; 660
• DOI: 10.1016/j.ces.2020.116429
• Languages: English
• ISSNs: 0009-2509

Abstract

Graphical abstract: Highlights: The coexistence of Lewis acid/base sites in the IL-ZIF was confirmed. The density of Lewis acid/base sites was tuned easily. A high yield of 97% was achieved over an IL-ZIF catalyst. Lewis acid/base sites reduce the energy barrier to 11.5 kcal mol −1 . A synergistic catalysis mechanism was confirmed by theoretical calculations. Abstract: Ionic liquid (IL) immobilized zeolitic imidazolate framework (ZIF) catalysts (IL-ZIF-8) were prepared through grafting IL on a dual-ligand ZIF by a facile post-synthetic modification. The coordinately unsaturated Zn as Lewis acid sites and bromide ions as Lewis base sites were confirmed in the resulted IL-ZIF. The density of Lewis acid/base sites was tuned easily by content of mixed linkers in the framework and/or the IL loadings. The coexistence of Lewis acid/base sites remarkably improved the activity for cycloaddition of CO2 with propylene oxide, compared with parent ZIFs and IL. In the absence of any co-catalyst and solvent, the prepared IL-ZIF-8(0.3) obtained a high yield of 97% with good stability and reusability. Besides, a Lewis acid/base synergistic catalytic mechanism was proposed. The synergetic interaction of Lewis acid sites and Lewis base sites significantly reduces energy barrier of propylene oxide ring-opening to 11.5 kcal mol −1 and thus promotes the CO2 cycloaddition reaction.